Steam plant



July 25, 1939. c. G. wALLlN 2,l67,469

STEAM PLANT Filed Jan. 29, 1937 2 Sheets-Sheet 1 CZ b f h 77" .2 I

.lg I: CN d E el i lEAN 1 s f 9 20 rf e iz 14 Ma sb f b d CW E93 e\ 12 gJ /nventom Patente d July 25, 1939 UNITED STATES PATNT OFFICEApplication January 29, 1937, Serial No. 122,946 In Sweden January 21,1936 7 Claims.

The invention relates to a steam plant in which there is a large andsomewhat variable demand for low pressure steam. In accordance with theinvention high pressure steam is generated and is passed through a backpressure engine before being supplied to the low pressure oonsumers. Thepower developed by the engine may be used to generate electric energy tobe used to supply the demand for power in the plant, which may besubstantially constant. If the amount of electricity thus generated isnot sufficient, it may be supplemented by power obtained from an outsidesource, such as a power company.

Inasmuch as the flow of steam through the engine is dependent upon thedemand for low pressure steam, when such demand is low the steam fiowingthrough the engine will be capable of generating only a small quantityof electricity, and hence a large amount must be purchased from thepower company. However, in accordance with my invention, a low pressureaccumulator is connected to the exhaust of the engine and the chargingValve of this accumulator is regulated by the electrical output of thegenerator driven by the engine in such a way that, if the consumption oflow pressure steam is reduced and the consequent reduction in steam fiowthrough the engine causes a reduction in the power gen'- erated, thecharging valve is opened, thus permitting additional steam to fiowthrough the turbine and be stored in the accumulator. Such steam may beutilized thereafter to supply peaks in the demand for low pressuresteam. In this way the output of the engine may remain substantiallyConstant in spite of Varying demand for the low pressure steam exhaustedfrom the engine, while at the same time preventing waste of low pressuresteam.

Fig. 1 is a more or less diagrammatic view of an embodiinent of myinvention as applied to a cellulose plant;

Figs. 2 3 are diagrams representing certain conditions obtaining in theoperation of apparatus shown in Fig. 1; and

Fg. 4 is a more or less dagrammatic View of another embodiment of myinvention.

Fig. is a layout of a cellulose factory. An cxtraction back pressureturbine l, serves for power production, this turbine taking the steamfrom the high pressure line (i and supplying it to the intermediatepressure line fi which Supplies steam to the consuiner 5, the latterbeing shown as a preheater, and to low pressure line 8 for supplyingpaper machine l. Between lines 3 and 4 a high pressure accumulator 8 isinserted. To

line ll is connected a low pressure accumulator 9, in the charging pipeof which is arranged regulating valve w which is governed by theelectrical output regulator Il in such manner that the Valve begins toopen when the output of generator l2 has dropped to a minimum amount of,say, 1090 kw., and closes when the output of the engine rises above 1000kw.

The steam supply to the turbine from the high pressure line 3 isnormally not regulated, the turbine thus taking as much steam ascorresponds to the total consumption. When Valve l is closed the totalconsumption of steam by the turbine is determined by the demand of theplant for process steam. The flow of steam through the low pressurestage of turblne 2 is goVerne-:l by a reducing valve l3 the opening ofwhich corresponds to the steam demand of low pressure line 6 which inthe present example is assumed to be Constant.

In Figs. 2 and 3 the working period of steam plant and generator isindicatcd. A is variable steam consumption of the plant, B substantially'Constant steam production of the boiler, and C the output produocd bythe generator. Between times f1 and t the steam 'consumption is lowerthan the steam production of the boiler. During this period the excesssteam passes to the accumulator il if valve iii has been opened.Otherwise it passes to high pressure accumulator En the described plantthe excess steam during the period 'LH- tz is absorbed by the highpressure accumulator S, and it is assumed that at the point tz therequired minimum output of the generator is reached. As the demand ofconsumer 5 for low pressure steam is reducod, the charging Valve lll ofaccumulator il consequently opens at time tz and prevents a furtherreduction in the steam quantity ilowing through high pressure part l ofthe turbine. With de'creasing steam demand of the plant the steam supplyto accumulato-r E5 is increased by means of charging Valve il). Theproduced output thus takes the course according to line a-b-c-d-Aceordingly in Fig. 2 the steam quantity flowing through high pressurestage i is also indicated by o b--c-ct High pressure accumulator 8 takesup the quantity of steam represented by the area lying between straightline B and line b-c--d The steam quantity represented by the area lyingbetween line c-d and line A flows into the low pressure accumulator.

The steam thus aocumulatcd is thus available for use during periods,such as represented by the the 'to-h, when the demand for low pressuresteam is greater than the amount supplied by the .boiler. Use of theaccumulated steam during such periods reduces the boiler capacityrequired for any given plant.

Instead of being regulated in the manner described, the charging of theaccumulator might for instance take place in such a Way that first thelow pressure accumulator 9 is charged with the excess steam, the steamquantity represented by the area bordered by the lines b--e-c-b fiowinginto the low pressure accumulator, which at the point ta is filled. Atpoint ts the output of the engine is Constant (Fig. 3) and would thengradually decrease according to line eg.

With this mode of operation the distance dg would thus represent theadditional amount D of power to be supplied by an outside station.

In Fig. 1 a valve I4 connected to the low pressure line 6 is providedwhich opens if the low pressure accumulator 9 becomes fully charged toosoon and is hence unable to absorb more steam. In this case, when theelectrical minimum outlput is reached, valve M allows the excess steamto escape into the open (unless it can be used Somewhere else) in orderto prevent a further decrease of the engine output. This can occur, forinstance, if owing to a disturbance one of the paper machines l' goesout of action and hence does not require steam.

Fig. 4 illustrates another modification of the invention. Here theturbine consists of an extraction back pressure part 21 and a condensingpart 22. To the low pressure line 23 a hot water accumulator 24 isconnected. In the cold water supply pipe to the accumulator a regulatingvalve 25 is arranged which is governed by the output of generator 26. Ifthe output produced reaches a certain lower limit, valve 25 opens andallows water to enter accumulator 24. A valve 30 is disposed in the linebetween the exhaust of high pressure section 2| and accumulator 24 andis controlled by the pressure within the accumulator so as to open upona reduction in pressure, which is caused by the introduction of coldwater, to thus permit steam to be charged into the accumulator.Therefore steam from low pressure line 23 is condensed and the flow ofsteam through the machine increased, so that the output does not dropbelow the desired minimum amount.

In Fig. 4 it is further assumed that firing 28 of the steam boiler isregulated in accordance with the boiler pressure, as accumulator 24 doesnot equalize all fiuctuations and adjustment of the steam production tothe demand is necessary.

The scope of my invention is not to be limited by the above describedembodiments, which have been given by way of example only, but is to bedetermined by the appended claims in view of the prior art.

What I claim is:

1. In a steam plant, a source of steam, a back pressure steam engine, aConsumer connected to receive steam from the exhaust of said engine, anaccumulator connected to the exhaust of said engine, a Valve betweensaid engine and said accumulator, and means responsive to decreasing andincreasing power output, respectively, of said engine to open and close,respectively, said valve.

2. In a steam plant, a source of steam, a back pressure steam engine, aConsumer connected to receive steam from the exhaust of said engine, anaccumulator connected to the exhaust of said engine, a Valve betweensaid engine and said accumulator, an electric generator operated by saidengine, and means responsive to decreasing and increasing electric poweroutput of said generator to open and close, respectively, said valve.

3. In a steam plant, a source of steam, a back pressure engine having alow pressure condensing section of limited capacity and a high pressuresection, an accumulator arranged to receive steam from the high pressuresection of the engine, a valve between said high pressure section andsaid accumulator, and means responsive to decrease in the power outputof said engine below a predetermined value for opening said valve,whereby to cause steam from said high pressure section to be stored insaid accumulator.

4. In a steam plant, a source of steam, a back pressure steam engine, anaccumulator connected to the exhaust of said engine, a conduit forsupplying relatively cold water to said accumulator, a Valve .in saidconduit, and means responsive to decreasing and increasing power output,respectively, of said engine to open and close said Valve.

5. In a steam plant, a source of steam, a back pressure steam engine, anaccumulator connected to the exhaust of said engine, a conduit forsupplying relatively cold water to said accumulator, a valve in saidconduit, means responsive to decreasing and increasing power output,respectively, of said engine to open and close said valve, a valvebetween said engine and said accumulator, and means responsive to adecrease in pressure in said accumulator for opening the last mentionedvalve.

6. That improvement in the art of steam generation and utilization whichincludes generating comparatively high pressure steam, utilizing saidsteam to produce power in a prime mover, taking steam from the primemover and storing it in an accumulator when the power output of theprime mover falls below a predetermined value, thus causing an increaseof steam fiow through the prime mover in order to increase the poweroutput thereof.

7. 'I'hat improvement in the art of steam generation and utilizationwhich includes generating comparatively high pressure steam, utilizingsaid steam for the production of power in a prime mover, supplying steamdischarged from the prime mover to a low pressure steam Consumer andstoring steam discharged from the prime mover when the power outputthereof falls below a predetermined value to thereby cause an increasein the steam flow through the prime mover in order to increase the poweroutput thereof.

CARL GUNNAR WALLIN.

